JP2002363552A - Organometallic light-emitting material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide new electrophosphorescent materials which can be used in an organic light-emitting device. SOLUTION: New light-emitting materials provided are represented by formulas I and II E is any one of group 16 elements (including sulfur); M is any one of group 10 metals (including platinum); and R1 to R14 are each independently selected from the group consisting of H, halogeno, alkyl, substituted alkyl, aryl, and substituted aryl, with substituents selected from the group consisting of halogeno, lower alkyl and recognized donor and acceptor groups, while R1 can also be selected from (C≡C)n R15 (C≡C) represents a carbon-carbon triple bond (acetylide group); n is 1 to 10; and R15 is selected from alkyl, aryl, substituted aryl, and tri(alkyl)silyl]}.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] This application claims priority to US patent application Ser. No. 60 / 274,142, filed Mar. 8, 2001. The present invention relates to luminescent materials, which are essentially separate organometallic molecules that can be deposited as thin layers by vacuum evaporation and that can act as voltage phosphorescent emitters in high efficiency and high brightness organic light emitting devices (OLEDs).

[0002]

2. Description of the Related Art Tan and its co-workers (Tang and cowo)
rkers) reported for the first time a high performance organic light emitting device (OLED) in 1987 (Tang, CW, et al., A.
ppl. Phys. Lett. 51, 913 (1987)). Their discovery was based on the adoption of a multilayer structure comprising a light-emitting layer and a suitable organic substrate hole transport layer. Alq ₃ (q = deprotonated 8-hydroxyquinolinyl) is selected as the luminescent material, which can (1) be able to form thin films of 1000 ° or less uniformly using vacuum evaporation, (2) good It proved to be high-performance because it is a charge carrier and (3) it emits strong fluorescence. Since then, research on OLEDs and the materials used in these devices has prospered. In fact, almost every major chemical company in the optoelectronics world has demonstrated some benefit in OLEDs. Obviously, OLED technology has been noted in the Stanford Resources Market Report (by David E. Mentl
ey, "The Market Potential for Organic Light-Emitti
ng Diode Displays, "Commercial Report, available a
t http://www.stanfordresources.com), which is penetrating the market directly and rapidly. Cathode ray tube (CRT),
The appeal of OLEDs that challenge the traditional technologies of liquid crystal displays (LCDs) and plasma displays is

[0003] 1) low operating voltage, 2) thin monolithic structure, 3) emits light rather than modulate, 4) good luminous efficiency, 5) full color potential and 6) high contrast and resolution, Based on many features and benefits, including what was said. OLEDs are devices that are incorporated with organic semiconductors that can emit visible light upon electrical stimulation. O
The basic heterostructure of an LED is shown in FIG. The layers are
It may be formed by evaporation, rotary casting or chemical self-assembly. The thickness ranges from a small number of monolayers (self-assembled film) to about 1000-2000Å
Range. The construction of such devices is based on the use of layers of organic optoelectronic material that generally rely on optical emission, ie, the general mechanism responsible for radiative recombination of trapped charges. Under a DC bias, electrons are emitted from the cathode (usually Ca, Al, Mg-Ag) and holes are emitted from the anode (usually transparent indium tin oxide (ITO)) into the organic material, where , They, when applied, have an electron transport layer (ETL) and a hole transport layer (HT).
Across L), they preferably migrate until they encounter a molecule in the emissive layer and form a luminescent excited state (Frenkel exciton) which, under certain conditions, undergoes a radiation decay to give visible light. The electroluminescent material may be present in a separate emissive layer between the ETL and the HTL in a structure referred to as a multilayer heterostructure. In some cases, buffer layers and / or other functional layers are also introduced to improve device performance.
Alternatively, these OLEDs, which are the same material for which the voltage-emitting emitter functions as an ETL or HTL, are also referred to as single-layer heterostructures.

[0004] In addition to the luminescent materials present as a major component in the charge carrier layers (HTL or ETL), other available luminescent materials are present in those layers at relatively low concentrations as dopants to provide color tuning and efficiency. Improvements may be made. When a dopant is present, the main component material in the charge carrier layer may be referred to as a host. Ideally, the materials present as host and dopant have a high level of energy transfer from the host to the dopant, high efficiency and high brightness,
It is tuned to emit in a relatively narrow band concentrated near the selected spectral region. While high emission efficiency fluorescent emitters have been widely applied as dopants in OLEDs, phosphorescent emitters have been neglected in this area. However, the quantum efficiency of voltage fluorescent devices is limited due to the lower theoretical ratio of single excitons (25%) compared to triple excitons (75%) based on electron-hole recombination from electrical excitation. . In contrast, if a phosphorescent emitter is used, the potentially high energy / electron transfer from the hole to the phosphorescent emitter may result in significantly better voltage emission efficiency (Baldo, MA, et al. .,
Nature 395, 151 (1998) and Ma, YG, et al., Syn
th. Met. 94, 245 (1998)). Several phosphorescent OLED systems have been created and, in fact, have proven to be relatively efficient and bright.

It is desirable for OLEDs to be assembled using a material that provides voltage phosphorescence corresponding to one of the three primary colors, red, green and blue, which may be used as a component layer in a full color display device. . Such materials can also be used as films using vacuum deposition techniques that have been proven to be a common method of manufacturing high performance OLEDs that can accurately control the thickness of the light emitting layer. It is desirable to be able to deposit. In fact, the highest efficiency and brightness are Ir (ppy)
₃ Obtained with a green voltage phosphorescent device using (ppy = deproton 2-phenylpyridine) (15.4 ± 0.2% as external quantum efficiency, almost 100 as internal efficiency)
%, Maximum brightness 10 ⁵ Cd / m ² ) (Adachi, C., et.
al., Appl. Phys. Lett. 77, 904 (2000). An OLED that emits saturated red light based on a voltage phosphorescent dopant Pt (OEP) (H ₂ OEP = octaethylporphyrin) has been published and patented (Burrows, P.,
et al., US Pat. No. 6,048,630), but its maximum brightness is only about 500 Cd / m ² . Orange OLED
In the above, a cyclic metalated platinum (II) complex Pt (thpy) ₂ (thpy = deproton 2)
-(2-thioenyl) pyridine) and PVK (poly (N-vinyl) carbazole) as host are related patents (Lamansky, S., et al., WO 00/5767).
6). However, the Pt (I
I) The complex is not suitable for sublimation or vacuum evaporation,
Therefore, a rotating casting method that provides a high operating voltage was applied, and a quantum efficiency of 0.11% and a luminance of 100 Cd / m ² were obtained at 22 V.

[0006]

SUMMARY OF THE INVENTION The present invention provides a high performance OL
Novel organometallic luminescent materials used as voltage phosphorescent emitters or dopants in EDs. In particular, the present invention, when added in an effective amount to a suitable host material, including a luminescent compound, an electron transport compound and a hole transport compound, tunes the emission color in the near red range and improves device efficiency and Design of a family of phosphorescent emitters to increase brightness,
It relates to synthesis, properties and uses. In addition, the thermal stability of these phosphorescent emitters of the present invention is sufficient to effect sublimation and can be easily introduced into equipment using vacuum deposition methods, and is therefore completely prepared from vacuum deposited materials. A high performance voltage phosphorescent device is realized.

[0007]

The family of voltage phosphorescent emitters used in the present invention is an acetylide (alkynyl) complex of a platinum-containing group 10 metal having the chemical structure of formula I or II.

[0008]

Embedded image (Where E = elements of group 16 (including sulfur); M
= Metals of group 10 (including platinum); R _{1 to} R ₁₄ are
Each independently selected from the group consisting of hydrogen; halogen; alkyl; substituted alkyl; aryl; halogen, lower alkyl and substituted aryl having a substituent selected from the group consisting of recognized donor and acceptor groups; R
₁ is (C≡C) _n R ₁₅ (where (C≡C) is carbon-
Represents a carbon triple bond acetylide group, n is 1 to 10, and R ₁₅ can be selected from alkyl, aryl, substituted aryl and tri (alkyl) silyl). The elements of group 16 are known as VIA group elements, and the elements of group 10 are VI
It belongs to the IIB group.

Some of these complexes are thermally stable up to 400 ° C., as evidenced by thermal mass spectrometry. These complexes are good phosphorescent emitters, giving intense orange to red emission (λ _max 550-630 nm) in liquid solutions by photoexcitation and in OLEDs by electrical stimulation.

DETAILED DESCRIPTION OF THE INVENTION In general, the present invention provides compounds of the formulas I and II
And OLED applications. The claims of the present invention include methods for synthesizing these novel complexes and their use as luminescent materials. These OLED applications include OLEDs where these complexes are introduced as components by vacuum evaporation, spin casting or other device manufacturing methods. In the present invention, OLE
The luminescent material used as emitter or dopant in D is one or more metal-acetylides (metal-alkynyl)
Group. Alternatively, the luminescent materials used as emitters or dopants in OLEDs include one or more platinum-acetylide (platinum-alkynyl) groups. In one embodiment, the emissive material used as an emitter or dopant in the OLED can include a platinum atom coordinated with a tridentate ligand using one carbon atom and two nitrogen atoms. In another embodiment, the emissive material used as an emitter or dopant in the OLED comprises a deprotonated phenyl carbonion and a platinum atom coordinated with a tridentate ligand to yield 2,2'-bipyridine.

In an exemplary embodiment, a luminescent material used as an emitter or dopant in an OLED can have a chemical structure represented by Formula I or II.

Embedded image (Where E = elements of group 16 (including sulfur); M
= Metals of group 10 (including platinum); R _{1 to} R ₁₄ are
Each independently selected from the group consisting of hydrogen; halogen; alkyl; substituted alkyl; aryl; halogen, lower alkyl and substituted aryl having a substituent selected from the group consisting of recognized donor and acceptor groups; R
₁ is (C≡C) _n R ₁₅ (where (C≡C) is carbon-
Represents a carbon triple bond acetylide group, n is 1 to 10, and R ₁₅ can be selected from alkyl, aryl, substituted aryl and tri (alkyl) silyl). In one embodiment, the luminescent material can be deposited as a thin layer by sublimation or vacuum evaporation. In other embodiments, the luminescent material can be assembled into the OLED by spin coating or other methods.

The present invention generally relates to the synthesis and properties of a family of organometallic luminescent materials and their use in high performance OLEDs. These new complexes have several chemical and structural features, such as: 1) a cyclic metalated diimine complex of a group 10 metal containing platinum; 2) a neutral molecule; 3) a square planar coordination environment around the metal; 4) defined by (C ＾ N ＾ N). The tridentate ligand occupies three coordination sites, and 5) the acetylide (alkynyl) group occupies the fourth coordination site. Combining the structural and spectroscopic features of both diimines and cyclic metallated Pt (II) complexes [(C ＾ N ＾ N)
Pt (II)] complex type reported
((a) Lai, SW, et al., Inorg.Chem. 38, 4046 (19
99). (B) Cheung, TC, et al., J. Chem. Soc., Dal
ton Trans. 1645 (1996). (c) Lai, SW, et al., Org
anometallics 18, 3327 (1999). (d) Yip, JHK, et
al., Inorg. Chem. 39, 3537 (2000). (e) Neve, F.,
et al., Inorg. Chem. 36, 6150 (1997)). These results demonstrate that these complexes are good room temperature phosphorescent emitters in both solid state and liquid solutions. The relatively long-lived emission that occurs in the range of λ _max 530-800 nm is due to charge transfer from triplet metal to ligand ( ³ MLCT) or metal-metal to ligand ( ³ MMLCT). Assigned to excited state.

While the present invention will be described in detail with reference to particularly preferred embodiments of the invention, it will be understood that these embodiments are merely illustrative and that the invention is not limited thereto. . Complex Synthesis A number of tridentate cyclic metallated Pt (II) aryl acetylides with different substituents on the aryl ring, as shown in Formula I or II, were synthesized.

[0013]

Embedded image The synthesis method is shown in Scheme 1.

[0014]

Embedded image Scheme 1 The tridentate (C ＾ N ＾ N) ligand is synthesized by the Krohnke's method.
ethod) (Krohnke, F. Synthesis 1 (1976)). Various acetylenes are used in the Sonogashir Act
a's method) (Takahashi, S. et al. Synthsis 627 (198
0)). Cl-bond precursor [(C ＾ N ＾ N)
[PtCl] was prepared under stable conditions (Cont.
stable, e. wt al.J. Chem. Soc. Dalton Trans. 2251
(1992) and 443 (1990)). The desired complex is
It was synthesized by Cu (I) -organic amine-catalyzed reaction. For example, [(C ＾ N ＾ N) PtCl] (0.33 mmol) in a degassed dichloromethane (30 mL) solution
l), terminal acetylene (1 mmol) and Et ₃ N
(3 mL) was added to CuI (5 mg).
The suspension was stirred for 12 hours under a nitrogen atmosphere at room temperature without the presence of light. The resulting mixture was rotary evaporated to dryness. The crude product was purified by flash chromatography (neutral Al ₂ O ₃ , dichloromethane as eluent) and / or
Or purified by recrystallization from dichloromethane / diethyl ether. Examples are listed in Table I, but are not limited thereto.

[0015]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[0016]

[Table 5]

Complex Thermal Stability Ideally, the low molecular weight components used in OLEDs must be able to sublime and be stable under normal deposition conditions. Many of the complexes of the present invention are ~ 400
It is thermally stable up to 400 ° C. and decomposes as platinum metal only at temperatures above 420 ° C. (see TGA curves for complexes 2 and 15 in FIGS. 2 and 3, respectively). The observed thermal stability of these complexes disclosed in the present invention containing a tridentate cyclic metallization ligand is significant compared to the bidentate Pt (thpy) ₂ emitter disclosed by Ramski et al., Which is unstable in sublimation. Make a control.

Spectroscopic Properties of the Complex In the present invention, the linkage of the acetylide group to the (C ＾ N ＾ N) Pt (II) moiety, which neutralizes the positive charge concentrated on Pt (II) enhance stability of the complex, further, changing the ³ MLCT emission depth in color basis. Formula I
And II display strong orange to red light emission in liquid solution. Examples of characteristic absorption and emission bands of these emitters in the present invention are summarized in Table II. Table II Note that all data was collected at 298K in a degassed dichloromethane solution.

The absorption and emission spectra exemplified for complexes 2 and 15 are shown in FIGS. 4 and 5, respectively. The strong orange-to-red phosphorescence of the inventive complex with its stability to sublimation means that these materials can be used as emitters or dopants in high performance OLEDs.

Organic Light Emitting Devices Devices using the complex of the present invention, such as those assembled by Prof. ST Lee of the City University of Hong Kong, have a multilayer heterostructure as shown in FIG. All organic layers, including the platinum complex described above, were vacuum deposited on ITO substrates. NPB (N, N'-di-1-naphthyl-N, N'-diphenyl-benzidine) and Alq
₃ (q = 8-hydroxyquinolinyl) was used as the hole transport and electron transport layers, respectively. BCP (2, 9
-Dimethyl-4,7-diphenyl-1,10-phenanthroline, bathocuproine) was used to constrain excitons in the emission band. Magnesium silver alloy was used as the cathode. The selected Pt complex has a conductive host material CBP (4,4'-) as a phosphorescent emitter.
N, N'-dicarbazole-biphenyl). Optimal doping levels were adjusted at 2, 4 and 6% and electroluminescence from the Pt complex was observed. A number of examples are listed below to further illustrate the invention.

[0021]

EXAMPLES Example 1 Complex 2 was used as an emitter. Typical voltage emission spectrum, current-voltage (IV) and luminance-for a device with a doping level of 2%
The voltage (BV) curve and the luminous efficiency-current density curve are shown in FIG. Turn-on voltage: ~ 5V; Maximum brightness: 1
9600 Cd / m ^{2 at 2} V; maximum efficiency: 25 mA / cm ²
4.2 Cd / A. In the voltage emission spectrum, 56
Near the 0-630 nm band, a 430 nm peak was observed indicating poor energy transfer between host and dopant.

EXAMPLE 2 The performance of an apparatus using Complex 2 as an emitter at a doping level of 4% is shown in FIG. Turn-on voltage: ５5 V; Maximum luminance: 7900 Cd / m ^{2 at} 10 V; Maximum efficiency: 30 mA
2.4 Cd / A at / cm ² . At this doping level,
The energy transfer between the host and the dopant was saturated to avoid light emission from the host.

Example 3 Complex 3 was used as an emitter. The performance of the device with a doping level of 4% is shown in FIG. A deep-colored voltage emission was observed (λ _max), which is consistent with the tendency for phosphorescence exhibited by these complexes in a dichloromethane solution at room temperature.
580 nm). Turn-on voltage: ~ 5V; Maximum brightness: 1
4000 Cd / m ^{2 at 2} V; maximum efficiency: 20 mA / cm ²
At 1.4 Cd / A.

Example 4 A complex 16 was used as an emitter. The performance of the device with a doping level of 4% is shown in FIG. The electroluminescence is a vibratory structured emission spectrum (λ _max 610 nm, 660 n
m) was red. Turn-on voltage: ５5 V; Maximum brightness: 3200 Cd / m ² at 13 V; Maximum efficiency: 30
1.0 Cd / A at mA / cm ² . In general, organometallic luminescent materials such as those of formulas I and II of the present invention have proven to be novel voltage phosphorescent emitters applicable to highly efficient and bright orange to red OLEDs. .
Obviously, the embodiments of the invention disclosed herein are well suited to accomplish the above objects, and numerous modifications and other embodiments will be practiced by those skilled in the art, It is intended that the appended claims cover all such modifications and embodiments that come within the true spirit and scope of the invention.

[Brief description of the drawings]

FIG. 1 shows a general heterostructure of an OLED.

FIG. 2 shows a TGA curve of Complex 2.

FIG. 3 shows a TGA curve of Complex 15.

FIG. 4 shows the UV absorbance and emission spectrum of Complex 2 in dichloromethane at 298K.

FIG. 5 shows the UV absorbance and emission spectrum of Complex 15 in dichloromethane at 298K.

FIG. 6 shows a heterostructure of an OLED according to the present invention.

FIG. 7 shows the voltage emission spectrum, current-voltage (IV) and luminance-voltage (BV) and luminous efficiency-current density curves of a device using Complex 2 as an emitter with a doping level of 2%. Show.

FIG. 8 shows the voltage emission spectrum, current-voltage (IV) and luminance-voltage (BV) and luminous efficiency-current density curves of a device using Complex 2 as an emitter with a doping level of 4%. Show.

FIG. 9 shows the voltage emission spectrum, current-voltage (IV) and luminance-voltage (BV) and luminous efficiency-current density curves of a device using Complex 3 as an emitter with a doping level of 4%. Show.

FIG. 10: Voltage emission spectrum, current-voltage (IV) and luminance-voltage (BV) of a device using complex 16 as an emitter with a doping level of 4%.
And a luminous efficiency-current density curve.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Michael Chi-Wan Chang Hong Kong Pokhum Road 75 Fairview Court 9B F-term (Reference) 3K007 AB02 AB03 AB04 AB18 DB03 4H050 AA01 AA03 AB91 WB11 WB14 WB21

Claims (7)

[Claims] 1. A luminescent material for use as an emitter or dopant in an organic light emitting device, comprising one or more metal-acetylide groups coordinated to a metal. 2. A luminescent material for use as an emitter or dopant in an organic light emitting diode, comprising one or more metal-acetylide groups coordinated to platinum. 3. A luminescent material for use as an emitter or dopant in an organic light emitting diode, comprising a tridentate ligand coordinated to platinum using one carbon atom and two nitrogen atoms. (4) 2,2'-bipyridine and substituted 2,2'-
An emitter or dopant in an organic light emitting diode, including a tridentate ligand coordinated to platinum, using a diimine group selected from bipyridine and a deprotonated aromatic group selected from phenyl, aryl and heteroatom containing aryl Luminescent material for use as. 5. A luminescent material having the chemical structure of formula I or II for use as an emitter or dopant in an organic light emitting diode. Embedded image (Where E = elements of group 16 (including sulfur); M
= Metals of group 10 (including platinum); R _{1 to} R ₁₄ are
Each independently selected from the group consisting of hydrogen; halogen; alkyl; substituted alkyl; aryl; halogen, lower alkyl and substituted aryl having a substituent selected from the group consisting of recognized donor and acceptor groups; R
₁ is (C≡C) _n R ₁₅ (where (C≡C) is carbon-
Represents a carbon triple bond acetylide group, n is 1 to 10, and R ₁₅ can be selected from alkyl, aryl, substituted aryl and tri (alkyl) silyl). 6. A luminescent material according to claim 1, which can be deposited as a thin layer by sublimation or vacuum evaporation. 7. An organic light-emitting diode which can be assembled using spin coating or other methods.
The luminescent material according to any one of the above.